Hi L.,
I've had great success using EFT for this kind of problem. EFT is a simple tapping technique which works with your meridians-like acupuncture without the needles. You can see the points on my website-www.eft-ayurveda.com. Have her tap the side of her hand when you suspect a break out coming on and say something along the lines of:
"Even though I'm so excited (nervous, scared, mad, etc.) I get spots on my face I'm a good girl" Then go through the tapping points (you can tap on her too) saying so excited! These spots etc.
Often the hives will just disappear, and your daughter will feel alot calmer.
I realize this all may sound very foreign to you, but as a parent nothing has been more useful to know!
Best of luck,
Stephanie